The individual domino pieces of a set are usually called dominoes or tiles.
Dominoes are small, flat, rectangular-shaped game pieces. Many different materials over the centuries have been used to make dominoes, including plastic, wood, bone, ivory, and stone. Domino pieces are usually twice as long as they are wide and are usually made to be exactly half as thick as they are wide so that they can stand on edge without falling over. A domino may be of any size, but an ordinary domino is about one inch wide and two inches long.
Like a playing card, a domino has a face and a back. The back of each tile is either blank or decorated with a design. The face of each tile is divided by a line across the center separating the piece into two square halves. Numbers are represented in each half by spots, commonly called pips, or the absence of spots, which represents zero.
When dominoes are made, the pips are uniformly molded or drilled and then painted. Domino sets can be found in almost any color combination. However, the most common color combinations are white dominoes with black pips and black dominoes with white pips.
An individual domino is named for the number of pips it has on each half of its face. For example, a domino face with 3 pips on one half and 5 pips on the other half is called the 3-5 domino.
Dominoes with the same number of pips on each half of the face are known as doubles, or doublets. A single domino, also referred to as a combination domino, has a different number of pips on each half of the face.
All tiles in a set that have the same number of pips on one end make up a suit. For example, the 0-0, 0-1, 0-2, 0-3, 0-4, 0-5, and 0-6 make up the suit of zero. Each double belongs to only one suit; singles belong to two suits. For example, the 3-5 belongs to either the 3 suit or the 5 suit. In most domino games, the number of pips on a domino are added or subtracted for scoring purposes. In some domino games, however, the number of pips on a domino is used strictly for matching purposes.
The Domino Set
A set of domino pieces is sometimes called a deck.
The four most common domino sets are the double-6, double-9, double-12, and double-15 sets. The set is named after the domino in the set with the highest number of pips. Most domino games are designed to be played with the double-6 set. Many of the new and popular party games are designed to be played with the larger sets (double-9, -12, and -15 sets), allowing for a larger number of players. Most game rules, however, can easily be modified for play with a larger or smaller set of dominoes.
Every set of dominoes includes all possible combinations of two numbers, from zero (blank) up to the highest number of pips in the set (for example, 12 in a double-12 set), as well as a double for each suit. Each combination of pips occurs only once in a set. A standard double-6 domino set consists of 28 tiles: 7 doubles and 21 singles.
In a double-6 set, each number appears eight times: once each on six tiles and twice on the double tile.